Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$150.98	3.779%	$156.6855	$156.69	$156.70	$156.70
Purchase #2	$206.73	13.267%	$234.1569	$234.16	$234.15	$234.20
Purchase #3	$218.35	3.177%	$225.287	$225.29	$225.30	$225.30
Purchase #4	$137.77	6.422%	$146.6176	$146.62	$146.60	$146.60
Purchase #5	$41.55	9.616%	$45.5454	$45.55	$45.55	$45.50
Purchase #6	$237.75	7.874%	$256.4704	$256.47	$256.45	$256.50
Purchase #7	$243.32	5.511%	$256.7294	$256.73	$256.75	$256.70
7 purchase totals =	$1,236.45		$1,321.4922	$1,321.51	$1,321.50	$1,321.50